An image sensor is mounted on a unit for a writing optics of a light printer etc., or a reading optics of a scanner etc. As shown in FIG. 1, a contact image sensor comprises a rod-shaped light source 1, an imaging optics 2, and a light-receiving element (a line image sensor) 3. An original (or referred to as an image to be read) 4 is irradiated by the light from the rod-shaped light source 1 and the light reflected on the original 4 is detected by the light-receiving element 3 via the imaging optics 2. In the figure, reference numeral 5 designates a substrate.
As the imaging optics 2, a rod lens array composed of a plurality of gradient index rod lens or a planar lens array such as a planar microlens array etc. (refer to Japanese Patent Publication No. 202411/2003) is used.
In a scanner mounted on a copy machine, a cold-cathode tube having a low light directivity and high luminance has been generally used as a light source, because a scan for books etc. is required.
However, a cold-cathode tube utilizes material such as mercury having an adversary effect on circumstances, so that the displacement of a cold-cathode tube with a rod-shaped light source using an LED etc. has been considered.
Also, a planar lens array described above comprises a plurality of spherical or aspherical microlens arranged regularly in a predetermined pitch on a plate, and a transparent resin etc. is used for the material of which such a planar lens array is made. The important matter in such an imaging optics is to effectively prevent the generation of ghost and stray light which are causes for the degradation of image quality. For that purpose, the light which dose not contribute to imaging should not be incident on lenses, so that a light shielding film is formed on the surface of lenses.
However, it is impossible to prevent stray light from generating in a lens only by the formation of a light shielding film on the surface of lenses. In order to prevent stray light from generating in lenses, respective lenses should be isolated so that unnecessary light is not incident on a given lens from neighbored lenses. In a case that a planar lens array is fabricated by an integral molding such as an injection molding, a light shielding film may not be formed in a lens.